linux-kernel - Re: [PATCH 5/5] rtc: sc27xx: Always read normal alarm when registering RTC device

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Message-ID: <CAMz4ku+ObP5vUijEbzMFF3hBe+RaQoOv7O2JxhGbq6Qs-t+iCQ@mail.gmail.com>
Date:   Thu, 25 Oct 2018 09:57:15 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Mark Brown <broonie@...nel.org>, linux-rtc@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] rtc: sc27xx: Always read normal alarm when
 registering RTC device

Hi Alexandre,

On 25 October 2018 at 08:34, Alexandre Belloni
<alexandre.belloni@...tlin.com> wrote:
> Hello,
>
> On 18/10/2018 16:52:30+0800, Baolin Wang wrote:
>> When registering one RTC device, it will check to see if there is an
>> alarm already set in RTC hardware by reading RTC alarm, at this time
>> we should always read the normal alarm put in always-on region by
>> checking the rtc->registered flag.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>> ---
>>  drivers/rtc/rtc-sc27xx.c |    8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/rtc/rtc-sc27xx.c b/drivers/rtc/rtc-sc27xx.c
>> index 72bb002..b4eb3b3 100644
>> --- a/drivers/rtc/rtc-sc27xx.c
>> +++ b/drivers/rtc/rtc-sc27xx.c
>> @@ -415,10 +415,14 @@ static int sprd_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
>>       u32 val;
>>
>>       /*
>> -      * If aie_timer is enabled, we should get the normal alarm time.
>> +      * Before RTC device is registered, it will check to see if there is an
>> +      * alarm already set in RTC hardware, and we always read the normal
>> +      * alarm at this time.
>> +      *
>> +      * Or if aie_timer is enabled, we should get the normal alarm time.
>>        * Otherwise we should get auxiliary alarm time.
>>        */
>> -     if (rtc->rtc && rtc->rtc->aie_timer.enabled == 0)
>> +     if (rtc->rtc && rtc->rtc->registered && rtc->rtc->aie_timer.enabled == 0)
>
> Note that the driver should not access rtc->registered and
> rtc->aie_timer.enabled and this is a bit fragile.
> But, on the other hand, I currently don't have anything better to
> suggest. I was also planning to add an in-kernel API for multiple alarms
> but I'm not sure it will actually help in your case.

Yes, I understand your concern. I will glad to help to test if you
introduce new APIs for multiple alarms to see if they can help in our
case. Thanks.

-- 
Baolin Wang
Best Regards